The Brazil-born striker, who is a member of the Spain squad preparing for the World Cup, has long been identified by Mourinho as the player to provide a more regular supply of goals than Fernando Torres, Samuel Eto’o and Demba Ba were able to contribute last season.

Chelsea will pay around €43m for the striker, although a significant portion of the transfer fee includes agents' fees.

The move will also more than triple the wages of Costa, who is believed to earn around £50,000 a week at the Vicente Calderon Stadium. Chelsea will hand the 25-year-old a five-year contract worth £150,000 a week.

Representatives of the Londoners have held a series of meetings with Costa's camp in recent months and the set of talks around the two clubs' Champions League second-leg showdown closed the deal.

Costa emerged as Chelsea's top centre-forward target following an outstanding campaign for Atletico, who won La Liga as well as finishing Champions League runners-up.

The 25-year-old scored 36 times in 50 matches for his club in the recently completed domestic season and his 27-goal league haul was third only to Cristiano Ronaldo (31) and Lionel Messi (28).

Chelsea were keen to trigger the Brazil-born forward's release clause in January, when he was also being closely monitored by rivals Arsenal, but the player did not want to leave in mid-season.

Mourinho has made no attempt to hide his desire to recruit a blue chip centre forward amid doubts over the futures of Torres, Eto'o and Ba. At least two of the trio are expected to leave in the summer, while Romelu Lukaku will hold talks with Chelsea chiefs this summer following a season-long loan at Everton.

Chelsea have been active in the transfer market following the completion of the domestic season.

The Londoners have agreed a deal with Paris Saint-Germain to sell David Luiz for an initial €49m [£40m] although the French champions have yet to officially confirm the Brazilian’s arrival.

Mourinho is also looking for a new left-back and a new central midfielder following the departures of Ashley Cole and Frank Lampard. Chelsea’s top midfield target is Juventus’ Paul Pogba and they are also monitoring the situation of Cesc Fabregas.